Screen clamping mechanism



1956 H. c. POLLITZ 2,774,477

SCREEN CLAMPING MECHANISM Filed Dec. 6, 1954 41 Ham/a" a Po/lLzz $7M. m 4 b 7 @E if 2.7 5

United States Patent '9 SCREEN CLAMPING MECHANISM Harold C. Pollitz, Cedar Rapids, Iowa, assignor to Iowa Manufacturing Company of Cedar Rapids, Iowa, Cedar Rapids, Iowa, a corporation of Iowa Application December 6, 1954, Serial No. 473,400

" 2 Claims. (Cl. 209 403 The present invention relates to the construction of material gradation screens and, more particularly, is con cerned with the provision of novel and substantially improved clamping means for securing such screens to their supporting frame work. a In conventional practice, screens for controlling the size of materials such as crushed rock, coal, gravel, and other similar items are generally constructed of interwoven wire. This wire mesh screen is supported in a steel framework in a taut condition and, in order to prevent deformation of the screen under the weight of material being screened, spaced supports are ordinarily provided under the central portion of the wire mesh. In order to increase the screening capacity most modern day screens are constructed for mechanical agitation for which it is desired that the screen be maintained in a near fiat, taut condition.

In order to provide a taut screen of the type above indicated as desirable, many screen clamping devices have been contrived by those working in the art. However, to my knowl dg none of these prior art constructions provide an arrangementwhereby the application of stretching forcesto the peripheral edges of the screen simultaneously acts. to force the center of the screen downwardly against the screen supports. Instead, the constructions of which I am aware tend, upon tightening, to provide an upwardlyacting component of force at the center of the screen. In use, this upwardly acting component tends to cause the screen to bow slightly away from the supports. Although it has sometimes been the practice to raise the middle supports to provide a fully supported screen surface, such any arrangement still does not prevent separation of the screen from the supports. in the absence of more complete control.

According to the present invention a wire mesh screen is provided having ,upwardly turned wire ends throughout the peripheral edge of the screen. The upwardly, and slightly backwardly, turned ends arecaught upon the hooked end of a novelly' constructed clamping channel. Immediately below the turned up ends of the screen, a screen side support, extending along'the periphery of the screen, is rigidly positioned. The clamping channel is adjustably mounted in a free-floating manner and is positioned so that upon the application of tightening forces urging the channel outwardly relative to the screen, the hooked end of the channel will tendto puli the outermost extremity of the screen'upwardly and a point immediately inwardly of said outermost point downwardly against the screen side supports. This action causes a peripheral bendingmornent on the screen causing the center of the screen to be urged downwardly firmly against the screen supports thereby providing'an extremely rigid and substantially fiat s creen. Further, upon tightening operations subsequently the initial operation, the action of the clamping structure of the present invention is ideni al" hr sh ut the Wide. ran e of adjusted; positions such that the bending moment above described is always present to constantly position the screen in the desired manner with a downward force on the entire width of the screen.

It is, therefore, an object of the present invention to provide an improved clamping structure for screens wherein a taut, near flat screen surface may be maintained at all times.

A further object of the present invention is the provi-v sion. of a screen clamping device which provides a constant clamping action throughouta wide range of adjusted positions.

Yet a further object of the present invention is to provide a screen clamping construction whereby a wire mesh screen may be stretched while at the same time forcing the center portion thereof in a downward directlon.

A feature of the present invention is a screen-holding side channel having a hooked screen engaging edge constructed to engage the peripheral edge of the screen throughout a substantial area of the hook.

Another feature of the invention is a novel free floating side channel mouth for contacting the peripheral edges of a screen and to permit a substantially straight-line tightening action thereof.

Still another object of the invention is to provide a much simplified and yet highly effective improved wire mesh screen support and tightening apparatus therefor.

Still other and further objects and features of the present invention will at once become apparent to those skilled in the art from a consideration of the attached drawings wherein a preferred form of the present invention is shown by way of illustration and, wherein:

Figure l is a cross-sectional View of a near flat wire mesh screen taken along a line extending transversely thereof and illustrating a screen assembly in accordance with the concepts of the present invention;

Figure 2 is a cross-sectional view of the screen assembly shown in Figure 1 and taken along the line 11-11 thereof;

Figure 3 is an enlarged view of one side of the screen support and clamp shown in Figure l in an initial adjusted position; and

Figure 4 is another enlarged view of the screen support and clamping construction shown in Figure 1 in a more advanced state of tightening than shown in Figure 3.

As shown on the drawings: a

As may be seen from a consideration of Figures 1 and 2, a generally rectangular screen frame is provided comprising screen frame sides 10 and 11 rigidly connected by angle iron cross braces 12 and 13. The members 10, 11, 12 and 13 are preferably welded together to provide,- effectively, an integral rectangular steel framework.

As shown, each screen frame side. is provided with a longitudinally extending screen retainer or clamping channel 14, 15 which grip the peripheral edges of the screen 16 and rigidly secure the screen against the respective screen side supports 17. and 18 of a rectangular angle iron frame. At intervals along the length of the clamping channell i and 15, clamping bolts 20 are loosely: passed through slots 21 and 22 in. the clamping channel. and frame side channel 14 and 10, respectively. Likea wise, a longitudinally formed channel 23 is. secured to the screen frame side for supporting the side screen sup-L.

a in dampening vibration and noise. The end of the transversely extending wires of the screen 16 are bent upwardly as at 29 and slightly backwardly as at 30 to form a plurality of upstanding. retaining hooks. The clamp ing channel 14 is complementarily provided with a reversely arcuately formed bend. 14a and a slightly backwardly turned terminal edge 1415 which cooperates with the'curved portions 29 of the screen. 16.

As will be noted from a consideration of Figures 3 and 4, the upwardly deflected portion 14b of the clamping chan'nel I4 ends at a point higher than the lowermost point of the curvature at Ma throughout the range 'of normal adjustment. Accordingly, the screen 16 will at all times be contacted by both the terminal edge 14b and the curved portion 14a. Thistwo point contact causes a, downwardly acting, deflecting forceto be placed inwardly of the. peripheral edge of the screen ina manner described more fully below.

In operation, the screen 16 is installed between the screen frame side 10 and 11 by loosening the bolts 29 'to a point where the clamping channels 14 and 15 may of the force urges the screen firmly against the screen side support 17. This force is, however, oniy a biasing force rather than a positive one and, accordingly, upon the application of increasing forces by the bolt and in view'of the fact that the end 14a of the clamping chan nel 14 cannot move downwardly, the point 140 is forced to move, in asliding fashion, upwardly asthe point 14b moves-toward the side frame 10.

This combination sliding and pivoting motion of the clamping channel 14.causes,. in combination with 'the arcuate lower edgei14a and upturned terminal edge 14b,

the application of a bending moment at the edge of-the screen which urges the edge upwardly and the portion of the screen inwardly therefrom downwardly. This bending moment tends to further urge the center portion ofthe 'screendownwardly in firm contact with the supports 27, thereby maintaining the screen substantially flat and in firm contact 'with the screen support bumpers 28 at all times'and under all conditions of. tautness.

' It will beunderstood that while the screen 16 illustrated in the drawings is of heavy gauge metal and accordingly the upturned portions 29 and 30 are sufiiciently rigid to resist deformation during clamping, the present invention may also be applied to lightweight, fine, screens. In such instances the upturned ends 29 and 30may be reinforced by a sheet metal. envelope extending'substan- 'tially parallel tothe members 16 and 17 and taking the general configuration of the outside peripheral" edge of -the..screen. Such a sheet metal reinforcement may,.if

' desired, be weldedto the screen and extended along only one surface thereof, or, alternatively, may extend around the outside. 'of-the screen and be folded backw'ardly over the ends 30 to's'andwich the upturned portions 29, 30'

between a folded-over reinforcing sheet metal channel. a

As an additional method'of construction, a longitudinally extending bar having an inwardly turned attachment lip or the likemay be welded to the peripheral edge of the screen 16- thereby serving the purpose of, and substitut ing for, the integral upturned portions 29, 30. 7

Theabove clamping action is very beneficial and is a substantially contrary to the ordinary practice in which no peripherally upwardly acting; bending moment giving a downward force in the middle of the screen is applied to the screen. In the absence of such a peripheral bending moment, forces applied horizontally outwardly to upturned screen ends cause a reverse bending moment to be applied. Such a reverse bending moment actually urges the center of the screen upwardly as the clamping.

action is increased, thereby providing a tendency forthe screen to separate from the supports 27:, Such separation causes instability in'the screen surface causing premature failure and poor screening,

it will, therefore, clearly appear that I have provided a greatly improved clamping device for screens or the i like wherein the clamping action provides. a peripheral bending moment tendingto. urge the center of the screen. downwardly against the screen supports. Since'tt will j be understood that variations and modifications can be made relative to the above structure without departing from the novel concepts of the present. invention, it IS intended that the scope, of the invention be limited solely by the appended claims.

I claim as my invention:

' 1. Screen tightening apparatus for positioning a screen in a plane comprising in combination, a peripheral support frame surrounding said screen, a plurality of screen supports attached to said frame and having one surface thereof positioned in 'said plane for supporting said screen at a plurality of points, first means associated with said frame for attachment to the peripheral edge of said screen, second means for drawing said first means upwardly and outwardly toward said frame, third means for contact with said screen on the opposite side thereof from said support and inwardly from the peripheral edge of said screen'for urging the central body of said screen downwardly securely against said supports when said secondmeans is drawn toward said frame, and fourth means positioned substantially under said third means'on the side of said screen opposite from said third means for contact with said screen whereby'drawing said second means toward said frame clamps said screen tightly against said fourth means at a point inwardly of the peripheral edge of the screen. ,1 V r V .7 I

' 2. Screen tightening apparatus for positioning a screen in a plane comprisingin combination, a peripheral stipport frame surrounding said screen, a plurality of screen supports attached to said frame and having one surface thereof positioned in'said plane 'for supporting said 7 screen at a. plurality of centrally located points, a first 'means associated with said frame for attachment to the peripheral edge of said screen, secondmeans'for draw ing-said first means upwardly and outwardly toward said frarngthird means for contact with'said screen on the opposite side thereof from said support and inwardly from the point of attachment of said first means for urging the central body of said screen downwardly securely against said supports when said second means is' drawn towardsaid'frame, and fourth means positioned substantially under said third means on theside of said screen I opposite from said third means for. contact'with said screen whereby drawingsaid second means toward said frame clamps said screen tightly against' said fourth means at a point inwardly of the peripheral edgeof'the screen,'said first means comprising an upwardlyand outwardly turned edge secured'to aclarnping channelsecured to said frame bysaid second means only and carrying'said third means. I i

References Cited in the file .of this patent f V V UNITED STATES 2,183,991 7 Hasman Dec'. 19, :1939

2,345,947 7 Parks Apr. 4, 1944 2,630,225

Sturtevant Nov. 15,. 1921 Bye Mar. 3', 19 53 

